Which substance can be added to paint to reduce the tendency toward skinning?

The correct answer involves understanding the role of antioxidants in paint formulations. Antioxidants are compounds that inhibit oxidation, a chemical reaction that can lead to the formation of a skin or film on the surface of paint as it dries. When paint is exposed to air, oxidation can cause it to skin over, forming a hardened layer that may complicate application and finish.

Adding antioxidants to paint helps mitigate this drying and oxidation process, allowing for better workability and extended pot life. This is particularly important in environments where paints are expected to be stored for longer periods before application or in climates where temperature fluctuations can accelerate skin formation.

While thixotropic additives modify the flow of paint to enhance application properties, they do not directly address skinning issues caused by oxidation. Similarly, fungicides are intended for preventing mold and mildew growth rather than influencing the drying characteristics. Surfactants can help improve the wetting and spreading of paint but are not primarily focused on preventing skin formation. Thus, the role of antioxidants makes them the appropriate choice for reducing skinning tendencies in paint.